Many different orthopedic casting materials have been developed for use in the immobilization of broken or otherwise injured body limbs. Some of the first casting materials developed for this purpose involve the use of plaster of Paris bandages consisting of a mesh fabric (e.g., cotton gauze) with plaster incorporated into the openings and onto the surface of the mesh fabric. Plaster of Paris casts, however, have a number of attendant disadvantages, including a low strength-to-weight ratio, resulting in a finished cast which is very heavy and bulky. Furthermore, plaster of Paris casts typically disintegrate in water, thus making it necessary to avoid bathing, showering, or other activities involving contact with water. Such disadvantages, as well as others, stimulated research in the orthopedic casting art for casting materials having improved properties over plaster of Paris.
A significant advancement in the art was achieved when polyisocyanate prepolymers were found to be useful in formulating a resin for orthopedic casting materials, as disclosed, for example, in U.S. Pat. No. 4,502,479 (Garwood et al.) and U.S. Pat. No. 4,441,262 (Von Bonin et al.). U.S. Pat. No. 4,502,479 sets forth an orthopedic casting material comprising a knit fabric which is made from a high modulus fiber (e.g., fiberglass) impregnated with a polyisocyanate prepolymer resin such as polyurethane. Orthopedic casting materials made in accordance with U.S. Pat. No. 4,502,479 provide significant advancement over the plaster of Paris orthopedic casts, including a higher strength-to-weight ratio and greater air permeability. Since the polyisocyanate prepolymer resin is generally formulated to be activated with water the aforementioned casting products are often provided to the user in the form of a "kit" comprising an air and water impermeable package and a roll of casting tape therein. The package is generally constructed of a multilaminate film material.
U.S. Pat. No. 4,667,661 (Scholz et al.) discloses a casting tape which further comprises a lubricant. The lubricant serves to provide a casting material which after being dipped in water is easy to apply and slippery to mold without the resin sticking to the gloved hands of the applier.
Unfortunately, the lubricant upon contact with the package also makes the outer surface of the package slippery. This reduces the "grip" a user can achieve on the edges of the package when he or she attempts to tear open the package. In many cases the grip is so reduced that the user is unable to easily exert the necessary tear force. Therefore, in order to open the package the user must either change his gloves or completely wash his hands and/or the outer surface of the package. Alternatively, the user may opt to open several packages at once (i.e., before letting the lubricant contact his gloved hands) and avoid this "slip" problem. However, this method has the disadvantage that the user must estimate the number of rolls needed for a particular therapy before beginning the therapy. In the event that the number of rolls is underestimated the slippery problem is not avoided. In contrast, in the event that the number of rolls is overestimated these extra rolls are needlessly exposed to atmospheric moisture and premature cure, and are therefore wasted.
From the foregoing, it will be appreciated that what is needed in the art is a kit of orthopedic casting material which has both the advantages of a slippery resin and an easy open package which may be easily opened even when contacted by a lubricant. It would be a further advancement in the art to provide this kit in a cost effective manner. Such kits of orthopedic casting material and methods for preparing the same are disclosed and claimed herein.